NORFOLK, Va. -- Moving a Norfolk-based aircraft carrier to Mayport, Fla., could cost less than half of what the Navy estimated it would, according to a federal report.

The U.S. Government Accountability Office estimates the cost of moving a carrier to be between $258.7 million and $356 million. The Navy had previously estimated it would cost more than $537 million to upgrade the Florida base so it could be the home port for a nuclear powered carrier.

Norfolk is the only home port for aircraft carriers on the East Coast. Defense officials say that's a national security concern, citing threats of terrorism and natural disasters.

Mayport lost the conventionally powered John F. Kennedy in 2007, when it was decommissioned.

Virginia leaders are concerned about a possible move because the Hampton Roads region stands to lose 6,000 jobs, half of those sailors aboard a carrier, and $425 million in annual revenue if a carrier permanently sails to Mayport.

The state's congressional delegation has called the proposal unnecessary and costly at a time when there are other pressing needs.

The GAO report released on Thursday criticized how the Navy estimated its cost, saying it failed to conduct a comprehensive, well-documented and credible analysis.

The biggest difference between the GAO estimate and the Navy's involves the cost of building new facilities at Mayport. The GAO puts the cost of building a controlled industrial facility at $70.5 million and for ship maintenance support facilities at $45.6 million.

The Navy estimates those costs at $139.1 million and $157.2 million, respectively.

The Navy said the difference in costs is because it factored in the cost of protecting buildings from a potential storm surge that may come from a Category 4 hurricane. The GAO also said it included a hurricane factor in its estimate, but they used different methods.

"Without fully meeting the characteristics of a high-quality estimate, the Navy's ability to present a convincing argument of the estimate's affordability and credibly answer decision makers' and oversight groups' question about the estimate is hampered," the report said.

"This is fantastic news for the First Coast and for Mayport's national security mission," Rep. Ander Crenshaw (R-
Fla.) said.